Add sync error logging, extend error flash, fix unload saves

- Log workforce sync errors to backend stdout so they appear in docker logs
- Extend error flash from 5s to 15s so errors are readable
- Replace sendBeacon (POST-only) with keepalive fetch (PUT) on unload —
  sendBeacon was hitting 404s on all three unload saves

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/node_modules/lucide-react/dist/esm/icons/cloud-upload.mjs

@@ -0,0 +1,18 @@
+/**
+ * @license lucide-react v1.24.0 - ISC
+ *
+ * This source code is licensed under the ISC license.
+ * See the LICENSE file in the root directory of this source tree.
+ */
+
+import createLucideIcon from '../createLucideIcon.mjs';
+
+const __iconNode = [
+  ["path", { d: "M12 13v8", key: "1l5pq0" }],
+  ["path", { d: "M4 14.899A7 7 0 1 1 15.71 8h1.79a4.5 4.5 0 0 1 2.5 8.242", key: "1pljnt" }],
+  ["path", { d: "m8 17 4-4 4 4", key: "1quai1" }]
+];
+const CloudUpload = createLucideIcon("cloud-upload", __iconNode);
+
+export { __iconNode, CloudUpload as default };
+//# sourceMappingURL=cloud-upload.mjs.map